/Engine/Source/Runtime/Core/Public/Containers/SortedMap.h
Add all items from another map to our map (if any keys are in both, the value from the other map wins).
template<typename OtherArrayAllocator, typename OtherSortPredicate> void Append ( const [TSortedMap](API\Runtime\Core\Containers\TSortedMap)< [KeyType](API\Runtime\Core\Containers\TSortedMap\KeyType), [ValueType](API\Runtime\Core\Containers\TSortedMap\ValueType), OtherArrayAllocator, OtherSortPredicate > & OtherMap )